The present invention relates to systems which are used for repairing defects in vessels and other lumens. More particularly, the present invention relates to methods and systems for the endovascular repair of a vascular defect, while simultaneously stabilizing the vascular site at which an intraluminal graft is attached.
Aneurysms are discrete dilations of the vascular wall. One of the most common, and among the most life threatening, is an aneurysm of the abdominal aorta between the renal and iliac arteries. If untreated, the aneurysm dilates progressively with an ever increasing risk of rupture and hemorrhagic death.
One method of treatment is provided by direct surgical intervention, in which the defective vessel may be bypassed or entirely replaced using a prosthetic device such as a synthetic graft. The risks involved in direct surgical intervention of this magnitude are great, and include an extensive recovery period.
In recent years a less invasive method of treatment has evolved through a series of inventions. The details vary, but, conventionally, a resilient tubular conduit fashioned from flexible fabric (herein referred to as a xe2x80x9cgraftxe2x80x9d) is introduced into the defective vessel by means of catheters introduced into the femoral artery. The graft is attached to the non-dilated arteries above and below the aneurysm using expandable metallic cylinders (herein referred to as xe2x80x9cattachment systemsxe2x80x9d) which may include barbs or hooks to assist attachment to the vascular wall. Conventionally, an attachment system is attached to the interior of the graft""s lumen.
However, the use of tubular grafts to reinforce vascular walls in a patient is attended by numerous complications. The most troubling long-term complications include difficulty in forming an adequate connection of the graft to the vascular wall, which may result in fluid leakage around the exterior of the implanted graft, and downstream migration of the graft. There are certain factors which contribute to these complications. In particular, there may be a slow but steady increase in the diameter of the vessel at the site of a stent-graft attachment, particularly when the attachment system is self-expanding, and it is not yet clear whether the diameter reaches a stable limit. As a result of this steady increase in the vascular diameter, an attachment to the vessel which might initially be adequately secure will tend to loosen, increasing the probability of graft migration and fluid leakage around the graft.
Accordingly, there exists a need to stabilize a vessel being repaired against gradual dilation, and to enhance the connection between a repair device and the vascular wall. The present invention addresses these needs.
Briefly, and in general terms, the present invention provides a system and method for endovascular repair involving vascular stabilization of a repair site. It is contemplated that aortic stabilization may be achieved by first implanting at a desired location within the vessel of a patient a substantially rigid stent, or a vascular support structure configured such that it does not have a tendency to continue to expand after implantation. A graft is thereafter contemplated to be implanted within the vessel at the repair site.
It has been discovered that when a stent that does not have a tendency to continue to expand after implantation is deployed within a vessel of a patient there is an immediate increase in the diameter of the vessel accompanying expansion of such stent, but there is little change in the diameter of the vessel thereafter. Moreover, it has been discovered that such stabilizing structure is rapidly incorporated into the vascular wall by a process referred to as tissue ingrowth. The present invention harnesses this physiological behavior of the vessel.
In one aspect of the present invention, stabilizing structures embodying a substantially rigid stent, which has sufficient stiffness to retain a fixed expanded diameter, is deployed by endovascular insertion at a location within a vessel. The substantially rigid stent of the present invention is configured to have numerous orifices in its wall in its expanded state. These orifices facilitate incorporation of the stent into the vascular wall, and allow attachment systems of a subsequently implant graft to protrude through the wall of the stent. Next, a flexible tubular graft with an expandable attachment system is provided. The graft and the attachment system assembly is deployed by endovascular insertion within the vessel so as to allow the attachment system to engage the vessel. The attachment system may have hooks, or any protrusion, structure or surface treatment, that provides fixation of the graft and attachment system relative to the substantially rigid stent.
Once the substantially rigid stent is implanted in the corporeal vessel, the vessel maintains a constant diameter established by the diameter of the substantially rigid stent. Moreover, over a period of time, the vessel may incorporate the substantially rigid stent into its wall, thereby enhancing the resistance of the substantially rigid stent to downstream forces. Thus, the attachment system fixing the graft in place within the vascular lumen has the advantage of being provided with a stable foundation which eliminates the slow radial dilation of the vessel which might occur in the absence of such stent. Additionally, the structure of the substantially rigid stent may also reinforce the vascular wall in the downstream direction and provide the attachment system of a graft with additional mechanical support to resist downstream forces.
These and other objects and advantages of the invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings of illustrative embodiments.